The present invention is related to UBR routing in ATM networks. More specifically, the present invention is related to load balanced UBR routing of virtual circuits in ATM networks based on the bandwidth of the virtual circuits.
Asynchronous Transfer Mode (ATM) networks are networks that support Virtual Circuits (VCs) of various service categories of traffic such as Constant Bit Rate (CBR), Variable Bit Rate (VBR) and Unspecified Bit Rate (UBR). These different service categories have different traffic characteristics and are used for different purposes. ATM networks use link state routing for routing the VCs. One of the desirable features of a link state routing protocol is Load Balancing. The efficiency with which a link state routing protocol load balances VCs in an ATM network determines how congested the network becomes under heavy traffic. A routing protocol that efficiently load balances VCs would minimize congestion in the network.
Load Balancing issues for UBR are different from that of VBR and CBR. When VBR and CBR VCs are signaled in an ATM network, they are specified with the bandwidth requirement for each such VC. This requirement specification is then used to reserve the bandwidth for each VC in the network. For UBR VCs, the bandwidth requirement is not specified and no bandwidth reservation is made in the network to support individual UBR VCs. The fact the UBR VCs do not have a bandwidth specified makes it harder to load balance UBR connections sensibly in ATM networks.
Connections are signaled as UBR connections either because their bandwidth requirement is unknown or, in the case where their bandwidth requirement is indeed known, they do not suit the other traffic characteristics such as the distribution of cell inter-arrival times of other service categories. In the case where the estimated bandwidth requirement of UBR VCs is known, this estimated bandwidth value can then be used to load balance UBR connections efficiently.
The present invention pertains to a system for sending data. The system comprises a telecommunications network which supports connections, each connection having a first attribute. The first attribute is that the connection has unspecified traffic. The network comprises switches, and links which connect the switches. The system comprises a routing module connected to the switches. The routing module has a mechanism for attributing a second attribute associated with transmission to each connection on the network. The second attribute is different than the first attribute. The routing module forms connections on the network based on the first attribute and the second attribute.
The present invention pertains to a method for sending data. The method comprises the steps of defining a telecommunications network which supports a connection having a first attribute. The first attribute is that the connection has unspecified traffic which travels on the connection. Then there is the step of attributing a second attribute associated with transmission to the connection on the network. The second attribute is different than the first attribute. Next there is the step of forming the connection on the network based on the first attribute and second attribute.